Histology of Cartilage, Bone and Joints Flashcards
1
Q
What is cartilage made of?
A
Chondrocytes
Extracellular matrix
2
Q
What makes cartilage?
A
Chondrocytes
3
Q
What do chondrocytes secrete?
A
Extracellular matrix
4
Q
What are the types of cartilage?
A
Hyaline
Elastic
Fibrocartilage
5
Q
Which type of cartilage is the most common?
A
Hyaline
6
Q
What is the general structure of hyaline cartilage?
A
Homogenous, amorphous matrix encased in perichondrium
7
Q
What is the perichondrium?
A
Thin outer layer of cartilage
8
Q
What are the properties of hyaline cartilage?
A
Low friction surface
Lubrication of synovial joints
Distributes applied forces
9
Q
What are lacunae?
A
Spaces within extracellular matrix of cartilage
10
Q
Where are chondrocytes within cartilage?
A
In lacunae
11
Q
What does the extracellular matrix of hyaline cartilage consist of?
A
Mainly type II collagen Proteoglycans = large glycosaminoglycans, including - Chondroitin sulphate - Keratan sulphate - Hyaluronate Chondronectin
12
Q
What is chondronectin?
A
Glycoprotein Binds - Collagen - Aggrecans - Integrins
13
Q
What is elastic cartilage?
A
Hyaline cartilage with addition of elastin
14
Q
Where is elastic cartilage found?
A
Ears
Ear canals
Epiglottis
Larynx
15
Q
What are the properties of elastic cartilage?
A
Very flexible
Maintains shape
16
Q
What does fibrocartilage do?
A
Binds solid joints
Forms meniscus and intervertebral discs
17
Q
What is fibrocartilage made of?
A
Dense connective tissue (type I)
Isolated islands of cartilage
- Type II collagen in matrix
- Dispersed chondrocytes
18
Q
Does fibrocartilage have a perichondrium?
A
No
19
Q
What are the properties of fibrocartilage?
A
Resists compressive and shearing forces
20
Q
In which bones is there a marrow cavity?
A
Long bones
21
Q
What does the marrow cavity contain?
A
Bone marrow
Fat
22
Q
What makes the dense wall of bone?
A
Compact bone
23
Q
What makes the “spongy” interior of bone?
A
Cancellous/trabecular bone
24
Q
What is the periosteum?
A
Bone surface covered with thin layer of connective tissue
25
What are the two layers of the periosteum?
Outer fibrous layer
| Inner more cellular layer
26
What is in the outer fibrous layer of the periosteum?
Fibroblasts
Blood vessels
Collagen
27
What is in the inner more cellular layer of the periosteum?
Osteoprogenitor cells
28
What type of bone forms the shaft of the long bone?
Compact bone
29
What is the structure of compact bone?
Outermost and innermost (lining marrow cavity) part in concentric layers
Rest formed by osteons/Haversian systems
30
What is an osteon/Haversian system?
Cylindrical modules
31
What is the organisation of trabecular bone compared to compact bone?
Less organised
32
What is trabecular bone made of?
Lamellae but not Haversian systems
33
What are the spaces in trabecular bone like?
Continuous
| Full of marrow and blood vessels
34
What does the medullary cavity contain?
Marrow
35
What types of marrow are there?
Red
| Yellow
36
When is red marrow present?
Early in life
37
What is red marrow made of?
Mainly haematopoietic cells
38
When is yellow marrow present?
Later in life
39
What is yellow marrow made of?
Mainly fat cells
40
Does yellow marrow have any haematopoietic cells?
Yes, preserves some
| Can become active haematopoietic tissue if needed
41
What do the blood vessels have instead of capillaries?
Sinusoids
42
What is the endosteum?
Covering over bone lining marrow cavity
43
Compare endosteum and periosteum
Endosteum thinner
Both have osteoprogenitor cells
Endosteum has fibrous element
44
How do arteries supply bones?
At discrete points
Branch in marrow cavity
Supply shaft and ends separately
Periosteum separately supplied
45
How do nerves supply bones?
Abundant
| Follow blood vessels
46
What is the diaphysis?
Bone shaft
47
What is the epiphysis?
Bone end
48
What cells do osteoprogenitor cells develop into?
Osteoblasts
49
What cells do osteoblasts develop into?
Osteocytes
50
What cells do osteocytes develop into?
Bone lining cells
51
What is the origin of osteoprogenitor cells?
Mesenchymal stem cells
52
What is the origin of osteoclasts?
Granulocyte/macrophage cell origin
53
What is the usual state of osteoprogenitor cells?
Resting/quiescent
54
Why do osteoprogenitor cells give rise to new osteoblasts?
Grow/repair bone
55
Where are osteoprogenitor cells found?
Periosteum
| Endosteum
56
What is the shape of osteoprogenitor cells?
Flattened
57
Where are osteoblasts found?
On bone surface of both compact and trabecular bone
58
What do osteoblasts do?
Secrete bone matrix
59
What is in the bone matrix secreted by osteoblasts?
Type I collagen
Bone matrix proteins
- Ca binding proteins = osteocalcin, osteonectin
- Adhesive proteins = sialoproteins, osteopontin
- Proteoglycans
- Alkaline phosphatase
60
What are markers of osteoblast activity?
Osteocalcin
| Alkaline phosphatase
61
What shape are osteoblasts?
```
Active = cuboidal/polygonal
Inactive = flattened
```
62
What happens to osteoblasts as deposition of matrix occurs?
Become surrounded by matrix > become osteocytes
63
What happens to some osteoblasts?
Become periosteal/endosteal bone lining cells
64
What are osteocytes?
Mature bone cells
| Surrounded by bone
65
Where are osteocytes found?
Sit in lacunae
66
How do osteocytes communicate with each other?
Via canaliculi (not visible with H&E)
67
What do osteocytes do?
Maintain bone in response to loading
68
What happens if osteocytes are lost?
Bone resorption
69
Why can you sometimes see white spaces around osteocytes histologically?
Destroy local bone to free calcium
70
What is the shape and size of osteoclasts?
Giant multinuclear cells
71
What do osteoclasts do?
```
Destroy bone in
- Growth
- Repair
- Normal turnover = remodelling
Release calcium
```
72
Where are osteoclasts found?
Seal themselves to bone around edge
73
How do osteoclasts break down bone?
Secrete
- Protons from H2CO3 breakdown
- Proteases
74
What is a marker of osteoclast activity?
Tartrate-resistant acid phosphatase
75
What nutrient is bone a major reservoir for?
Calcium
76
What increases blood calcium?
Osteoclast/osteocyte activity
77
What decreases blood calcium?
Osteoblast activity
78
What controls calcium homeostasis?
Hormones from
- Thyroid gland
- Parathyroid gland
79
What types of bone are laid down during development?
Membranous
| Endochondral
80
What is intramembranous ossification?
Membranous bone forms directly from mesenchyme
81
Which bones undergo intramembranous ossification?
Skull
Flat bones of face
Mandible
Clavicles
82
What is endochondral ossification?
Cartilage model of bone produced
| Cartilage replaced by bone
83
Which bones undergo endochondral ossification?
Weight bearing bones
| Bones of extremities
84
What are the steps of endochondral ossification?
1. Bone collar forms around diaphysis
2. Cartilage beneath collar degenerates
3. Blood vessels invade, bring in bone cell progenitors = 1st centre of ossification
4. 2nd centre of ossification appears in each epiphysis
5. Zones of ossification grow together but leave thin zone of cartilage = growth plate
6. Growth plate lost with age
85
What does the growth plate do?
Enables long bones to grow
86
When does the growth plate fuse?
21-22 years
87
What are the zones of the growth plate?
```
Resting
Proliferative
Maturation
Hypertrophic
Ossification
```
88
What type of bone is new bone, either during development or repair?
Woven bone
89
How is woven bone different to compact and trabecular bone?
More cellular
More collagen
No Haversian systems
90
What cells remodel woven bone?
Osteoclasts
| Osteoblasts
91
How does remodelling occur via Haversian systems?
```
Osteoclasts make new cavities in bones
Along stress axis
Blood vessels and endosteum invade
Osteoblasts line new space
Lay down layer of bone
```
92
What are synovial joints?
Joints where bones move freely against each other
93
What creates the joint space?
Connecting bones outside articular cartilage with synovial membrane
94
What type of cartilage is articular cartilage?
Hyaline
95
What are the properties of articular cartilage?
Slippery
Smooth
Resistant to compression
No perichondrium
96
What is in the synovial space?
Synovial fluid
97
What does the synovial fluid do?
Lubricates
| Provides nutrients
98
What lines the synovial space?
Synovial membrane
99
What is the synovial membrane?
Not epithelium
100
What is the structure of the synovial membrane
```
No
- Basement membrane
- Tight junctions
- Desmosomes
Surface layer = intima
- 2-3 cells thick
- Mix of fibroblast-like and macrophage-like synoviocytes
Sub-intimal layer
- Connective tissue
```
101
What is synovial fluid made of?
Ultrafiltrate from synovial blood vessels
| Proteoglycans
102
What is the structure of intervertebral discs?
```
External ring of fibrocartilage = annulus fibrosis
Nucleus pulposus
- From notochord
- Forms gelatinous centre
- Type II collagen
- Replaced by fibrocartilage by age 20
```
